\begin{table}%t2
\caption{The MXU multi-slit instrumental set-up.} 
\label{chip}
%\centerline
 {\begin{tabular}{lcc}
\hline\hline
 Run                        & Run 1 + 2                       & Run 3 + 4  \\
\hline                      
 Telescope                  & \multicolumn{2}{c}{VLT--UT4}               \\
 Instrument                 & \multicolumn{2}{c}{FORS2}                  \\
 Mode                       & \multicolumn{2}{c}{MXU (i.e.\ mask multi-slit)} \\
 Grism                      & \multicolumn{2}{c}{GRIS$\_$600RI+19}       \\
 Filter                     & \multicolumn{2}{c}{GG435}                  \\
 Spectral resolution        & \multicolumn{2}{c}{6.6$~${\AA}  {\it FWHM} }    \\
 Detector(s)                & Site                 & 2 $\times$ MIT \\
 Detector size              & $2048 \times 2048$   & $2 \times (2048 \times 1024)^{a}$ \\
 Pixel size                 & 24~$\mu$m $\times$ 24~$\mu$m  & 30~$\mu$m $\times$ 30~$\mu$m$^{a}$ \\
 Readout noise              & 5.41~e$^{-}$         & 3.15~e$^{-}$        \\
 Conversion factor          & 1.91~e$^{-}$/ADU     & 0.70~e$^{-}$/ADU    \\
 MXU slit width             & 1\farcs0             & 1\farcs0            \\
 Spatial scale              & 0\farcs20/pixel      & 0\farcs25/pixel$^{a}$     \\
 Dispersion                 & 1.32$~${\AA}/pixel  & 1.66$~${\AA}/pixel$^{a}$ \\ 
 Wavelength range$^{b}$ & 5300--8000$~${\AA}  & 5120--8450$~${\AA}           \\
\hline
\end{tabular}}
\par
$^{a}$~After binning the CCDs by $2 \times 2$, which is the default.\\
$^{b}$~For a slit at the centre of the field of view.
\par
\end{table}